The objectives of this proposal are to define the impact of AN on bone turnover in adolescent females. We hypothesize that there is A) disordered bone metabolism in AN demonstrated by reduced biochemical markers of bone formation and/or increased markers of bone resorption B) abnormal peak bone mass accretion during puberty in AN subjects wherein BMD is reduced early in the disease and remains low even in late puberty, and C) the proposed low BMD and abnormal bone turnover in AN subjects during puberty can be correlated with low body mass index (BMI), disease severity, delayed skeletal maturation, and low levels of insulin-like growth factor 1 (IGF-1) and estradiol (E2).